1. Field of the Invention
Achieving faster, better and/or more reliable methods and analyzers for determining the quality of liquids containing polyphenols is of interest in many fields. One of these fields concerns the determination of the role of polyphenols in wine quality. Polyphenols are called tannins in certain liquids, such as wine. They have the property to bind to and precipitate proteins. They are composed of a very diverse group of oligomers and polymers1. Current research direction involves attempts to determine the relationship between tannin structure and “mouthfeel” of red wines. Tannins contribute two characteristics to red wine: 1) astringency and 2) bitterness. Tannins are thought to cause increased friction between mouth surfaces and a sense of dryness or roughness. The term “mouthfeel” has been used to describe the sensation of wine in the mouth and it is now recognized as an important property of red wine quality. Researchers are trying to correlate mouthful properties of different tannins with their structure and composition.
2. Description of Related Art
U.S. Pat. No. 6,874,357 describes a method for determining the mechanical impedance of a test liquid drop set on the surface of a piezoelectric resonator of ultrasound frequencies which is designed for excitation of the drop during the drying-up time of the drop. The time dependence of the mechanical impedance of the drop is a sensitive parameter used to assess the quality of liquid products. This patent describes other patents (U.S. Pat. Nos. 2,137,126, 2,007,716, 2,127,430 and 5,798,452) that use similar methods for testing liquid quality and points out their shortcomings. It is recognized that the key to successful production of high quality red wine is effective tannin management. Viticulture decisions can influence the extent and nature of polyphenols that find their way into the wine. Wine makers decide on how to macerate red grapes so as to achieve the right level of polyphenol extraction. Parameters that can be manipulated include temperature of fermentation, pumping over or “punching down” the cap, choice of fermentation vessel and other variables. The presence of polyphenols or tannins in the wine product has an impact on wine flavor and overall quality. This effect has been difficult to characterize chemically and with the use of sensors. Phenols influence taste, odor, color and clarity. In the past, gas chromatography was used exclusively to measure volatile constituents in wine. Besides gas chromatography, there is High Pressure Liquid Column (HPLC) chromatography that can be used to measure monomer and polymer phenols including all major constituents in wine3. Polyphenols or tannins influence mouthfeel and their presence can be measured by HPLC chromatography4. There are other optical devices that could be used to measure the amount of polyphenols in the liquid product including photometers. Photometers (for example HANNA Instruments HI83742 Photometer) are available in the marketplace that can measure the concentration (grams/liter) of total phenols in wine. The measurement of the concentration of phenols in wine could be useful for determining the relationship of total phenols concentration with quality. However, the use of this type of photometer requires adding chemical reagents to the wine sample and waiting for a chemical reaction to occur before measuring the concentration of total phenols in wine. In addition, this photometer is limited to only wine products. Polyphenols play a role in the quality of other products. Notable sources of polyphenols include berries, tea, beer, olive oil, chocolate/cocoa, coffee, pomegranates, fruits and fruit based drinks